XK469, 2-[4-(7-chloro-2-quinoxalinyloxy)phenoxy]propionic acid, is among the most broadly active antitumor agents that have been evaluated in our laboratories. The agent is currently in development in a collaborative effort between the National Cancer Institute, the DuPont Corporation and our laboratories with expectations for clinical trial to begin in 2000. The objectives of the project are to elicit incisive information on the mechanism of action of XK469 and to improve the therapeutic index of the lead agent through (1) a comprehensive synthetic program of congeners and bioisosters of XK469 to (a) identify the active centers of the lead compound, i.e., the pharmacophore, which is responsible for the high solid tumor selectivity exhibited by this agent and (b) to improve such limitations as toxicity and host recovery times, among others observed in the evaluation of XK469 in mice; (2) an evaluation of all newly synthesized analogs in an in vitro, disk-diffusion-soft agar-colony-formation-assay to determine the cytotoxicity of each agent against leukemias, solid tumors and normal cells. Analogs that exhibit solid tumor selectivity will be evaluated in tumor-bearing mice for in vivo efficacy. Analogs demonstrating high activity will then be evaluated in mice carrying a variety of tumors of both mouse and human origin, utilizing, in addition, SCID mice for human tumors.; (3) corroboration, through synthesis, of structures assigned by mass spectrometry to mouse-urinary metabolites of XK469; (4) the use of structure-activity data to establish quantitative structure activity relationships, using the methodology of comparative molecular field analysis (CoMFA) as the basis for the design of novel compounds of predicted high activity; (5) an investigative exploration of the modes of cytotoxic action of XK469 and its analogs; and (6) determine the effect of XK469 on selected molecular targets.